[Qemu-devel] [PATCH 4/6] This patch converts v9fs_write() to make use of the threadlets infrastructure.

[Arun R Bharadwaj <arun@linux.vnet.ibm.com>]

From: Gautham R Shenoy <ego@in.ibm.com>

This patch offloads all the blocking calls invoked for v9fs_write onto the
helper threads belonging to the threadlets infrastructure. The handling of
the v9fs_post_*write* calls is done from the io-thread context.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 hw/virtio-9p.c |   63 ++++++++++++++++++++++++++++----------------------------
 hw/virtio-9p.h |    5 ++++
 2 files changed, 37 insertions(+), 31 deletions(-)

diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index da185c3..5fb7dc4 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -2459,37 +2459,41 @@ out:
     return;
 }
 
-static void v9fs_write_post_pwritev(V9fsState *s, V9fsWriteState *vs,
-                                   ssize_t err)
+/************************ v9fs_write calls ************************/
+
+static void v9fs_write_do_pwritev(ThreadletWork *work)
+{
+    V9fsWriteState *vs;
+
+    vs = container_of(work, V9fsWriteState, work);
+    v9fs_do_pwritev(vs->s, vs->fidp->fs.fd, vs->sg, vs->cnt, vs->off);
+    vs->v9fs_errno = errno;
+
+    v9fs_async_helper_done(vs->post_fn, vs);
+}
+
+static void v9fs_write_post_pwritev(void *opaque)
 {
-    if (err  < 0) {
+    V9fsWriteState *vs = (V9fsWriteState *)opaque;
+
+    if (vs->err  < 0) {
         /* IO error return the error */
-        err = -errno;
+        vs->err = -errno;
         goto out;
+    } else {
+        vs->off += vs->len;
     }
     vs->total += vs->len;
     vs->sg = adjust_sg(vs->sg, vs->len, &vs->cnt);
     if (vs->total < vs->count && vs->len > 0) {
-        do {
-            if (0) {
-                print_sg(vs->sg, vs->cnt);
-            }
-            vs->len = v9fs_do_pwritev(s, vs->fidp->fs.fd, vs->sg, vs->cnt,
-                      vs->off);
-            if (vs->len > 0) {
-                vs->off += vs->len;
-            }
-        } while (vs->len == -1 && errno == EINTR);
-        if (vs->len == -1) {
-            err  = -errno;
-        }
-        v9fs_write_post_pwritev(s, vs, err);
+        v9fs_do_async_posix(&vs->work, v9fs_write_do_pwritev, &vs->post_fn,
+                            v9fs_write_post_pwritev);
         return;
     }
     vs->offset += pdu_marshal(vs->pdu, vs->offset, "d", vs->total);
-    err = vs->offset;
+    vs->err = vs->offset;
 out:
-    complete_pdu(s, vs->pdu, err);
+    complete_pdu(vs->s, vs->pdu, vs->err);
     qemu_free(vs);
 }
 
@@ -2539,7 +2543,6 @@ static void v9fs_write(V9fsState *s, V9fsPDU *pdu)
 {
     int32_t fid;
     V9fsWriteState *vs;
-    ssize_t err;
 
     vs = qemu_malloc(sizeof(*vs));
 
@@ -2548,19 +2551,20 @@ static void v9fs_write(V9fsState *s, V9fsPDU *pdu)
     vs->sg = vs->iov;
     vs->total = 0;
     vs->len = 0;
+    vs->s = s;
 
     pdu_unmarshal(vs->pdu, vs->offset, "dqdv", &fid, &vs->off, &vs->count,
                   vs->sg, &vs->cnt);
 
     vs->fidp = lookup_fid(s, fid);
     if (vs->fidp == NULL) {
-        err = -EINVAL;
+        vs->err = -EINVAL;
         goto out;
     }
 
     if (vs->fidp->fid_type == P9_FID_FILE) {
         if (vs->fidp->fs.fd == -1) {
-            err = -EINVAL;
+            vs->err = -EINVAL;
             goto out;
         }
     } else if (vs->fidp->fid_type == P9_FID_XATTR) {
@@ -2570,21 +2574,18 @@ static void v9fs_write(V9fsState *s, V9fsPDU *pdu)
         v9fs_xattr_write(s, vs);
         return;
     } else {
-        err = -EINVAL;
+        vs->err = -EINVAL;
         goto out;
     }
     vs->sg = cap_sg(vs->sg, vs->count, &vs->cnt);
     if (vs->total <= vs->count) {
-        vs->len = v9fs_do_pwritev(s, vs->fidp->fs.fd, vs->sg, vs->cnt, vs->off);
-        if (vs->len > 0) {
-            vs->off += vs->len;
-        }
-        err = vs->len;
-        v9fs_write_post_pwritev(s, vs, err);
+        vs->err = vs->len;
+        v9fs_do_async_posix(&vs->work, v9fs_write_do_pwritev, &vs->post_fn,
+                            v9fs_write_post_pwritev);
     }
     return;
 out:
-    complete_pdu(s, vs->pdu, err);
+    complete_pdu(vs->s, vs->pdu, vs->err);
     qemu_free(vs);
 }
 
diff --git a/hw/virtio-9p.h b/hw/virtio-9p.h
index fcea434..be87d5f 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -343,6 +343,11 @@ typedef struct V9fsWriteState {
     struct iovec iov[128]; /* FIXME: bad, bad, bad */
     struct iovec *sg;
     int cnt;
+    V9fsState *s;
+    int err;
+    int v9fs_errno;
+    ThreadletWork work;
+    void (*post_fn)(void *arg);
 } V9fsWriteState;
 
 typedef struct V9fsRemoveState {